The XW 2E and 2F or CAS 3E and 3F (Chinese Amateur Radio satellite 3E and 3F) are two identical picosatellites for amateur radio mission only. These satellites are built on an 116 mm × 116 mm × 116 mm cubic body, similar to a 1U CubeSat, but not complying to the CubeSat specifications. The have a mass of approximately 1.5 kg mass each. The amateur communications payload consists of U/V 20 kHz wide transponders with 145 MHz CW beacon and 19k2 GMSK AX25 telemetry downlinks.